Generally speaking, a hydraulic system uses a fluid under pressure to operate or actuate a control member. A common lawn sprinkler is a simple hydraulic system which uses pressurized fluid (water) to mechanically operate the sprinkler head to rotate or reciprocate. Another pervasive example of a hydraulic system is the braking system commonly found on cars and trucks. A common type of automotive hydraulic braking system has a reservoir (“master cylinder”) filled with brake fluid. Stepping on the brake pedal pressurizes the fluid in the reservoir and forces the pressurized fluid through tubes (“brake lines”) that lead from the reservoir to each of the vehicle's wheels. The pressurized fluid actuates braking mechanisms on each wheel (e.g., disk calipers for disk brakes and/or brake pad contact with wheel drums for drum type brakes) to slow or stop the vehicle. Such hydraulic systems have proven to be reliable, lightweight, relatively easy to maintain and capable of providing good control.
Because of these and other advantages, aircraft have also long used hydraulic systems for a number of control applications including for example landing gear, brakes, steering, drag braces, flight controls, and the like. Typically an aircraft hydraulic system includes a pressurized reservoir and a hydraulic circuit containing a desired amount of hydraulic fluid. While such systems are generally quite reliable, it is possible that they can and will lose fluid over time. Loss of fluid can result in system misoperation, components failure and unscheduled maintenance.
Loss of hydraulic fluid typically occurs over time and at a very slow rate. While periodic inspection of the hydraulic system is desirable, it would also be desirable to automatically detect and monitor the amount of hydraulic fluid contained within the hydraulic system, and to automatically detect, measure and indicate the loss of hydraulic fluid in order to monitor system health.
Sensors are often used to monitor hydraulic system operation. In a car or truck, a sensor can be used to monitor the pressure the system is applying to the brake lines. Aircraft typically have more complex sensor systems including for example a quantity gauge to measure the quantity of fluid in the low pressure reservoir chamber, a pressure transducer and a temperature transducer.
Some known aircraft based systems gather large amounts of data and/or use a number of sensors whose main purpose is to estimate leakage and/or implement “built in tests”. One example system estimates leakage using high frequency sampling rate pressure sensors located at pump discharge duct. Another known system sets the hydraulic system in a desirable operational condition and compares pump rotation to a reference value based on previous pump operational tests without leakage. A further exemplary system installs hydraulic flow sensors at the supply conduit and return conduit to provide an indication of leakage at each “consumer” (e.g., actuator or other hydraulically operated device).
While much more has been done in the past, further improvements are desirable. One area for improvement is to provide a predictive system that can automatically warn concerning potential failures so corrective action can be taken before failures actually occur.
Exemplary illustrative non-limiting methods and systems herein provide analytical techniques for processing data obtained from onboard sensors, such as temperature indication and reservoir quantity indication.
The relationship between fluid temperature and reservoir level indication can provide for the estimation of mass of fluid of the entire system. This estimated value can be stored. By means of historical values of the current estimation, it is possible to obtain a value indicative of system fluid leakage.
An exemplary illustrative non-limiting implementation is also capable of determining and predicting future values of reservoir quantity or/and fluid mass of the entire system.
One exemplary illustrative non-limiting system works on a system architecture that can be applied to a number of prognostics and health monitoring solutions. The results from this solution can be presented (e.g., displayed) using an exemplary illustrative non-limiting user interface.